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EROSION

EROSION. The process by which sediments are obtained and transported. Erosion involves a transporting system with several components:. AGENT OF EROSION- (e.g. stream, glacier, wave, current, wind, or human activity). 2. SEDIMENTS BEING MOVED. 3. DRIVING FORCE.

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EROSION

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  1. EROSION The process by which sediments are obtained and transported. Erosion involves a transporting system with several components: • AGENT OF EROSION- (e.g. stream, glacier, wave, current, wind, or human activity). 2. SEDIMENTS BEING MOVED 3. DRIVING FORCE

  2. The DRIVING FORCE behind most types of EROSION is GRAVITY

  3. Mass Wasting The downward movement of material under the influence of gravity is called mass wasting. Water can play an important role, but gravity is the main element

  4. MASS WASTING INVOLVES TWO MAJOR OPPOSING FORCES 1. FORCE OF GRAVITY – constant downward pull 2. FORCE OF FRICTION – attempts to keep objects in place Gravity > Friction – movement Gravity < Friction – no movement Gravity = Friction (equilibrium) – no movement

  5. Oh no!

  6. Factors that resist gravity include the materials strength and cohesion vegetation internal friction between grains Angle of underlying rock Factors that help gravitational forces increasing the slope angle under cutting of the slope amount of weathering amount of water moving through material overloading slopes with new material

  7. Mass wasting is often caused by a force that temporarily disturbs the slope equilibrium • Earthquakes • Heavy rain • Leakage from water pipes and swimming pools • Volcanic eruptions • explosions • thunder

  8. Excavation at the base of a slope can lead to slope instability i.e. road cut along slopes

  9. The angle at which the underlying rock is inclined has a major impact on mass wasting.

  10. Slides: These are slow to rapid movement of material along one or more surfaces. Slumps areUsually slow to moderate in speed Movement along a curved surface Usually in unconsolidated materials like soil Rockslides are rapid to very rapid movement along a planar surface

  11. A Slump

  12. Slumpcaused by erosion in southern California

  13. Mass wasting occurs when rocks weather at a higher elevation and fall to a lower elevation. This is called, (you guessed it), a Rock Fall

  14. Rock Falls: Free falling rock from steep mountain sides. Usually caused by ice wedging. Any sized material may fall. The collected debris at the bottom is called TALUS

  15. Talus Slope or Rock fall

  16. In real life, landslides can be quite destructive: Rate = 1 mm/day to 1 km/hr Houses can be totally covered by sand and mud, like this:

  17. This landslide tragically took the life of many unsuspecting woodland creatures.

  18. Types of landslides

  19. Flows: These are mass movements where the material moves as a viscous fluid or plastic movement Mudflows are very rapid and contain a lot of water and mud Earthflows are slow to moderate movement of material down a slope which leaves an exposed scrape. Solidification is the slow downward movement of water saturated soil. Common in areas of permafrost Creep is extremely slow movement of soil & rock downhill

  20. Mud Flows happen faster (1-5 km/hr) THE PROBLEM WITH LANDSLIDES AND MUDSLIDES IS THAT THEY ARE OFTEN UNPREDICTABLE AND CAN BE VERY DAMAGING TO LIFE AND PROPERTY

  21. Mud Flow

  22. Solidifluction:in Alaska

  23. “Soil creep” happens very slowly (less than 1 cm per year). Soil gradually moves downhill Soil creep

  24. Bent trees are the most obvious indicator of soil creep

  25. Creep

  26. Solutions to Mass wasting: Surface and subsurface drainage of hillsides Replanting of vegetation Reduce the angle of slope Putting in retaining walls and bolting rock faces

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